a little confused

I want to play with 1.5b but do I need a separate Jquery Enchant
download? Is Enchant its own plugin, and if so is it the old one I've
seen mention of on this list? Is it just the FX kit thats included
with the Jquery 1.2.3 download?
specifically, ... other than 1.5b and 1.2.3 ... do i need to download
anything else?